1. Field of the Invention
This invention relates to a display panel having a hermetically sealed space formed between two substrates, a method of manufacturing the display panel, and a partition wall included in the display panel.
The present application claims priority from Japanese Application No. 2002-345727, the disclosure of which is incorporated herein by reference.
2. Description of the Related Art
Display panels used in display apparatuses include a flat display panel designed to have a hermetically sealed space formed between two substrates, such as a plasma display panel (hereinafter referred to as “PDP”) and a field emission display panel (hereinafter referred to as “FED”).
FIG. 1 is a schematic front view illustrating the cell structure of a conventional PDP. FIG. 2 is a sectional view taken along the V—V line in FIG. 1.
The conventional PDP includes a front glass substrate 1, serving as the display screen of the panel, having a back surface on which a plurality of row electrode pairs (X, Y), a dielectric layer 2 covering the row electrode pairs (X, Y), and an MgO-made protective layer 3 covering the back surface of the dielectric layer 2 are formed in this order.
Each of the row electrodes X (Y) includes transparent electrodes Xa (Ya) each formed of a wide transparent conductive film made of ITO (Indium Tin Oxide) or the like, and a bus electrode Xb (Yb) formed of a metal film of a small width assisting the conductivity of the transparent electrodes.
The row electrodes X and Y are arranged in alternate positions in the column direction such that the transparent electrodes Xa and Ya of the respective row electrodes X and Y face each other with a discharge gap g in between, and each of the row electrode pairs (X, Y) forms a display line L in matrix display.
The front glass substrate 1 is opposite a back glass substrate 4 with a discharge-gas-filled discharge space S in between. On the back glass substrate 4, a plurality of column electrodes D are regularly arranged and each extend in a direction at right angles to the row electrode pairs (X, Y); a column electrode protective layer 5 covers the column electrodes D; a partition wall 6 formed in a shape partitioning the discharge space as will be described later; and red-, green-, and blue-colored phosphor layers 7 individually formed in such a way as to cover the column electrode protective layer 5 and the side faces of the partition wall 6.
The partition wall 6 is formed in a grid shape of transverse walls 6A and vertical walls 6B. Each of the transverse walls 6A extends in a row direction in a position opposite the bus electrodes Xb and Yb which are arranged back to back in between the respective and adjacent row electrode pairs (X, Y). Each of the vertical walls 6B extends in a column direction in a position opposite a midpoint between the two adjacent transparent electrodes Xa and between the two adjacent transparent electrodes Ya, the transparent electrodes Xa and Ya being lined up at regular intervals along the corresponding bus electrodes Xb and Yb of the respective row electrodes Y and X. The partition wall 6 defines discharge cells C in each of which the two transparent electrodes Xa and Ya of the row electrode pair (X, Y) face each other with the discharge gap g in between.
The partition wall 6 partitioning the discharge space into the discharge cells C is conventionally formed of insulating materials. For example, a thick coat of a partition wall material such as a glass paste or the like is applied on the back glass substrate 4 and then dried. Then, the resulting insulating materials undergo a sandblasting process through the medium of a mask, trimmed into a predetermined pattern, to be cut into the grid shape, and then a burning process for completion.
Such the foregoing conventional method of forming a partition wall is showed in JP Pat. Publication No. 2000-195431.
However, the conventional method of forming the partition wall with use of the sandblasting process has the problems of a degradation in productivity and an increase in manufacturing costs because of such a complicated manufacturing process.
Therefore, instead of the conventional partition wall formed by patterning the insulating materials, the use of metal-made partition wall covered with an insulating layer is suggested.
FIG. 3 is a plan view illustrating the structure of such a metal-made partition wall, and FIG. 4 is a side view illustrating the metal-made partition wall mounted on a substrate.
In FIG. 3, a metallic partition wall 10 having the surface covered with an insulating layer includes a portion 10A situated in a position corresponding to the display area of the display panel. The portion 10A has a matrix arrangement of through holes 10Aa opened therein and each having a quadrangular opening.
The display area portion 10A is surrounded by a flat plate-shaped portion 10B situated in a position corresponding to the non-display area of the display panel.
As shown in FIG. 4, the metallic partition wall 10 is arranged on the column electrode protective layer 5, covering the column electrodes on the back glass substrate 4 (see FIG. 2), so as to place each of the through holes 10Aa into a position for defining the corresponding discharge cell C.
After that, a burning process is performed so that the insulating layer of the metallic partition wall 10 is fused to the column electrode protective layer 5 to secure the metallic partition wall 10 onto the back glass substrate 4.
At this point, however, the following problems are produced in the metallic partition wall 10 structured as illustrated in FIG. 3.
During the burning process for securing the metallic partition wall 10 to the back glass substrate 4, in the display area of the display panel, a binder (resin component) and the like evaporates from the column electrode protective layer 5 and then emanates from the through holes 10Aa of the metallic partition wall 10. However, the non-display area of the display panel has no escape route for the binder evaporating from the column electrode protective layer 5 and emanating from the non-display area portion 10B of the metallic partition 10 which is sited in the non-display area. As a result, after completion of the burning process, a difference in thickness is produced between the portion of the column electrode protective layer 5 corresponding to the display area of the display panel and the portion of the column electrode protective layer 5 corresponding to the non-display area.
Because of the this difference in thickness, thus, there may be occurrence of disjoining between the metallic partition wall 10 and the column electrode protective layer 5 in the boundary portion between the display area and the non-display area of the display panel.